Time-switches for electric circuits, and particularly for signalling circuits



y 1936 J. M. VERNHES 2,757,257

TIME-SWITCHES FOR ELECTRIC CIRCUITS, AND PARTICULARLY FOR SIGNALLING CIRCUITS Filed Dec. 22, 1953 Fi0.1 O

I815 3 I1 A C 6 E"? Z L 52 W United States Patent Office 2,757,257 Patented July 31, 1956 TIME-SWITCHES FOR ELECTRIC CIRCUITS, AND

There has been described in Patent No. 2,515,407 an electric time switch applicable in particular to automobile signalling circuits comprising a contactor so arranged as to set up in an active position two circuits, one'of which includes a bi-metallic strip, a flexible blade and the utilization circuit, and the other one a resistance surrounding the bi-metallic strip, the end of said bi-metallic strip comprising a contact acting as a holding hook for the contactor as long as the bi-metallic strip is not moved away by the heating exerted on it by the resistance.

The present invention concerns an improvement in this type of time switches for electric circuits which, for instance, should control an electric signalling circuit for a predetermined period.

This improvement is characterized by a resistant bimetallic strip which is placed in circuit by means of a conductive pawl controlled by the user, said bi-metallic strip, due to its displacement by the pawl placing its two elastic conductive blades in contact which close the load circuit. The spring loaded pawl is placed in the required direction so that the bi-metallic strip, by heating up, releases the pawl, which places the bi-metallic strip out of circuit. When cooling slowly, the bi-metallic strip resumes its initial position while releasing, after a time, the elastic blades it has placed in contact. The latter separate owing to their elasticity and cut ofl the load circuit. One is back to the starting position and the user, by acting on the pawl control may start the operation again.

For limiting the current through the bi-metallic strip, a resistance is preferably placed in series in the circuit for the bi-metallic strip.

A description of one form of embodiment of the invention is given hereinafter with reference to the appended drawing wherein:

Figure 1 is a diagram of the time-switch, the load circuit being cut ofi.

Figure 2 is a similar diagram, the load circuit being closed.

Fig. 3 is a diagrammatic view similar to Fig. 1 but showing a modification.

The bi-metallic strip is a resistant strip having a fixed end at A. Its other end is free. In the vicinity of this end, the bi-metallic strip 1 carries a conducting contact stud 2 and a non-conducting stud 3. The direction of deformation of this bi-metallic strip when the temperature rises is indicated by the arrow F (Figure 1).

An elastic metallic blade 4 is secured at a point B, and its free end comes and rests on the stud 3 for all positions of the bi-metallic strip. This blade also carries a contact 5. The support B is connected with the load circuit represented by lamp 6.

Another elastic metallic blade 7, carrying a contact 8 arranged opposite the above contact is attached at one point C and rests, through its free end, on an adjustment screw 9. The support C is connected with the current source S. It is also connected with the support A for the bi-metallic strip, through a shunt 10, which, in practice, is a resistance R for limiting the current.

A pawl 16 is capable of being actuated by the handle of the switch. This pawl, pivoting about an axle 13 is brought back to its rest position by a spring 12. The pawl is also grounded.

A stop 15 may be provided for limiting the run of the bi-rn'etallic strip 1, in case of a low temperature.

The operation is as follows:

When the handle of the apparatus is actuated, the pawl assumes the position shown in Figure 2, deforming elastically the bi-metallic strip 1 and remains engaged behind the contact stud 2. At that moment, two circuits are set up. A first circuit C, 7, 8, 5, 4, B, 6 and ground (load circuit) and a second circuit C, 10, A, 1, 2, 16, 13 and ground.

The resistant bi-metallic strip then heats up rapidly, moves beyond the position of elastic deformation of Figure 2 and releases the pawl, cutting the circuit C, 10, A, 1, 2, 16, 13 and ground while keeping the power supply circuit connected.

The hot bi-metallic strip then begins to cool and grad ually comes back to its initial position. At a certain moment, the contact between 8 and 5 ceases, breaking the load circuit. The duration of the current flow through the load circuit is adjusted by acting on the adjustment screw 9.

Theoretically, the bi-metallic strip 1 could operate by its own resistance, 10 being a connection with no appreciable resistance; in practice however for using a suitable section for' the bi-metallic strip, the connection 10 is etfected by using a resistor R which limits the value of the current through the bi-metallic strip circuit.

As shown in Figure 3, a variation of the above-described apparatus consists in replacing the blade 4, Figure 1, by a bi-metallic strip 4 identical with the strip 1 and of opposite direction of deformation upon rise of temperature, as indicated by the arrow F. In such a case, the change in operating time which would result from too high an increase or decrease in ambient temperature is compensated due to its equal effects on the two bi-metallic strips.

What I claim is:

l. A time switch for an electric signalling circuit comprising a bi-metallic element one end of which is fixed and connected to the input to the electric circuit and the other end of which is movable and offers, on one side, a conducting contact point and, on the other side, an insulating contact point, an oscillating metal pawl capable of bending the bi-metallic element by pushing the conducting contact point, the direction of hot deformation of the bi-metal element when hot being that of this mechanical bending, a conducting elastic blade parallel with said bi-metal element, one end of which is fixed and connected to the utilization circuit and the other end of which is free and in constant contact with the insulating contact point on the bi-metal element, and a second conducting elastic blade parallel with the previous one, one end of which is fixed and connected to the input to the electric circuit and the other end of which is movable and carries a contact point coming in contact with the first blade when the bi-metal element is bent by the control pawl and by its deformation when hot.

2. A time switch for an electric signalling circuit comprising a bi-metal element, one end of which is fixed and connected to the input to the electric circuit and the other end of which is movable and offers on one side a conducting contact point and, on the other side, an insulating contact point, an oscillating metal pawl capable of bending the bi-metal element by pushing the conducting contact point, the direction of deformation of the bimetal element when hot being that of this mechanical bending, a conducting, elastic blade parallel with said bi-metal element, one end of which is fixed and connected with the utilization circuit and the other end of which is free and in constant contact with the insulating contact point of the bi-metal element, and a second conducting elastic blade, parallel with the above, one end of which is fixed and connected with the input to the electric circuit and the other end of which is movable and comprises a contact point coming in contact with the first blade when the bi-metal element is bent by the control pawl and by its deformation when hot, an adjustable stop for the return motion of the second blade and an adjustable stop for the cold bi-metal element.

3. A time switch for an electric signalling circuit comprising a bi-rnetal element, one end of which is fixed and connected with the input to the electric circuit and the other end of which is movable and ofiers, on one side, a conducting contact point and on the other side an insulating contact point, an oscillating metal pawl capable of bending the bi-metal element by pushing the conducting contact point, the direction of deformation of the bi-metal element when hot being that of this mechanical bending, a conducting elastic blade parallel with said bi-metal element, one end of which is fixed and connected with the utilization circuit and the other end of which is free and in constant contact with the insulating contact point on the bi-metal element, and a second, conducting elastic blade, parallel with the above, one end of which is fixed and connected with the input to the electric circuit and the other end of which is movable and carries a contact point coming in contact with the first blade when the bi-metal element is bent by the control pawl and by its deformation when hot, an adjustable stop for the return motion of the second blade and an adjustable stop of the cold bi-metal element, and a resistance limiting the current in the circuit of the bicapable of bending the bi-metal element by pushing the conducting contact point, the direction of deformation'of the bi-metal element when hot being that of this mechanical bending, a second bi-metal element identical with the above but with an opposite direction of deformation, one end of which is fixed in the vicinity of that of the first bi-metal element, and connected with the utilization circuit, and the other end of which is free and in permanent contact with the first bi-metal element, a conducting elastic blade, parallel with the above, one end of which is fixed and connected with the input to the electric circuit and the other end of which is movable and carries a contact point coming in contact with the blade when the bi-rnetal element is bent by the control pawl and by its deformation when hot.

References Cited in the file of this patent UNITED STATES PATENTS 

